Pre-heat your oven to 200C/180C Fan/Gas Mark 6. Line 10 muffin holes with cupcake/muffin liners.
In a small bowl, break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn't burn.
In a large mixing bowl, whisk together melted butter and both sugars. With an electric/stand mixer, go for a solid 3-5minutes so it is totally combined. Add in the eggs, one at a time and mixing in between.
Now, add the melted chocolate slowly (check it first, to make sure it isn't so hot that it will cook the eggs) and combine once again.
Add the flour and cocoa powder, fold gently into the wet mixture with a rubber spatula or wooden spoon until just combined. Fold in the chopped caramel chocolate. Scoop tablespoons of batter into each muffin hole, until just over 2/3 full - this should be about 9-10.
Bake 20-25 minutes, until the tops look crisp/shiny and are no longer wobbly. Let cool on a wire rack before serving!